The present invention relates to a sheet for sprouting grass seed and for safeguarding early grass growth and, more particularly, to an improved mat for growing lawns or other vegetation on soil. The seed sprouting sheet is made up of a vinyl plastic film with ventilation openings of a certain size and spacing. The ventilating holes, depending upon the grass sowing season are, optimally, approximately 3.5 cm to 4.5 cm apart and 9 mm to 15 mm in diameter.
For grass seeds to sprout in a secure environment adequate temperature and appropriate moisture on the surface or upper part of the ground has to be maintained. For the safe growth of young grass, warm temperatures have to be maintained for about six to seven weeks. Normally, the sowing season for grass seeds is from Spring to Summer. Thus, the sowing of grass seed is carried out when ground temperatures are lower than the required temperature for grass seed sprouting and young grams growth.
Grass seed is mainly sown by hand seeding and by a method known as xe2x80x9chydro-seeding.xe2x80x9d According to the hydro-seeding method, grass seeds are mixed in a dissolved fiber solution and are dispersed on the surface of the ground. In order to properly maintain the humidity on the soil surface for sprouting and growing new grass, continuous irrigation must be supplied. Where sloped surfaces are sown by the hydro-seeding method, the seeds along with the soil tend to be eroded by irrigation or rainfall and collect at the bottom of the slope. Consequently, the grass seeds do not sprout uniformly.
Alternatively, a mat can be placed on top of the sown grass to keep them warm and moist. Mats, however, do not solve the problem of soil erosion caused by rainfall or irrigation when planting grass seeds on slopes, hills or inclines. Because of this the grass seeds can not grow safely and uniformly.
Many forms of mat or carpet products which are intended for growing lawns and other forms of vegetation have been known in the art. These products have not gained acceptance due to failures in some aspect of their design. Often made of fibrous materials and mulching material mixed with seeds to be germinated, these compositions generally expand upon watering, causing the mulch material to break the adhesive bond with the fibrous structural material. The result is that the mat is broken down quite rapidly and large parts of it may be washed away. Further, many of the prior art mats fail to properly protect the seeds during germination and sprouting, exposing them to birds, wind and rain.
Prior art mats that are designed to prevent early mat degradation caused by watering still do not provide the benefits of the present invention. For example, U.S. Pat. No. 4,190,981 to Muldner discloses a laminated mat having a base sheet of water pervious web material, a bed of seeds and compressed peat particles as a middle layer, and an upper layer comprising a fibrous, porous veil. However, the upper layer is not designed to hold and maintain moisture levels nor is it shown to elevate ground temperatures to sprout and protect young grass seedlings. Mats of this type have also been known to be bulky and heavy. However, light-weight mats are also known. See, e.g., U.S. Pat. No. 5,765,304 to Clark. But unlike the present invention, Clark is directed to a mat where grass seeds are germinated, and the mat is then transferred, in the manner of sod, to a soil location once the seeds have sprouted.
It is therefore an object of the present invention to provide an improved grass seed mat to facilitate safe sprouting of grass and growth of young grass. It is also an object of the present invention to provide a grass seed mat that will enhance and maintain soil temperature to promote grass seed germination and growth. It is a further object of this invention to provide a grass seed mat having precise ventilation to control moisture as well as temperature. Other objects of the present invention include providing an improved grass seed mat to facilitate seeding of problem areas such as steep slopes, a grass seed mat of light weight and one that is easy and less costly to install.
In accordance with the above objects, the grass seed mat of the present invention generally stabilizes soil and reduces watering requirements while raising seedbed temperature to promote germination. The mat tends to keep the soil surface and upper soil layer in the range of about 26xc2x0 C. to 35xc2x0 C. and to supply adequate moisture and ventilation for the green seeds. The mat comprises a transparent vinyl sheet on its upper surface to control temperature and moisture. Preferably constructed of polyethylene (PE), the vinyl sheet used to cover the sprouting grass seeds has been found to maintain the soil surface and upper soil layer at just below 35xc2x0 C., even when the outside air temperature may fall to 20xc2x0 C. or 30xc2x0 C. But in the daytime, however, soil surface temperatures could rise to as high as 65xc2x0 C. to 70xc2x0 C. As a result the temperature between the ground surface and the vinyl sheet rises as well, causing the young grass to grow slender and weak, or become xe2x80x9csunburned.xe2x80x9d To moderate the effect of high temperatures, the vinyl sheet contains perforations of variable size and spacing to provide appropriate ventilation depending on soil and climatic conditions. These perforations, which also control moisture and evaporation thus reducing watering requirements, can be in the range of 6 mm to 18 mm, and are generally spaced apart 3.0 cm to 6.0 cm.
The construction of the mat of the present invention includes a base sheet of a carpet-like fabric which contains the grass seeds, or any type of plant or vegetable seeds, placed at certain intervals for maximum results. The base sheet also includes coated, polymer-type starter fertilizer and biodegradable, non-toxic adhesive for bonding the base sheet to a middle sheet of semi-transparent natural viscous cellulose fiber. The middle sheet is bonded to the top, vinyl sheet. A decomposing slow release fertilizer may be incorporated into the vinyl top sheet. All three sheets decompose by micro-organisms within six weeks, and should be stapled to the ground using biodegradable staples to secure against heavy winds and rain.
In some embodiments, the base sheet and middle sheet may be formed together as one layer, which is then bonded to the vinyl top sheet. In addition, a fibrous ground sheet may be added below the base sheet for the purpose of weed control. Further embodiments include additional sheets for weed and/or insect control.
The sowing method in accordance with this invention is to pick out the stones, tree roots and other foreign material and to make the ground flat and even. Next, the grass seed mat with vinyl sheet containing ventilation openings is spread out on the ground. The sheet containing grass seed, fibrous material and fertilizer comes into contact with the ground. Water is then added by sprinkling to thoroughly wet the grass seed mat, causing the mat to more uniformly and completely contact and adhere to the soil surface.